[PATCHv2 2/4] nvme-pci: Distribute io queue types after creation

[keith.busch@intel.com (Keith Busch)]

The dev->io_queues types were set based on the results of the nvme set
feature "number of queues" and the IRQ allocation. This result does not
mean we're going to successfully allocate and create those IO queues,
though. A failure there will cause blk-mq to have NULL hctx's because the
map's nr_hw_queues accounts for more queues than were actually created.

Adjust the io_queue types after we've created them when we have less than
originally desired.

Fixes: 3b6592f70ad7b ("nvme: utilize two queue maps, one for reads and one for writes")
Signed-off-by: Keith Busch <keith.busch at intel.com>
---
 drivers/nvme/host/pci.c | 46 ++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 40 insertions(+), 6 deletions(-)

diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c
index 98332d0a80f0..1481bb6d9c42 100644
--- a/drivers/nvme/host/pci.c
+++ b/drivers/nvme/host/pci.c
@@ -1733,6 +1733,30 @@ static int nvme_pci_configure_admin_queue(struct nvme_dev *dev)
 	return result;
 }
 
+static void nvme_distribute_queues(struct nvme_dev *dev, unsigned int io_queues)
+{
+	unsigned int irq_queues, this_p_queues = dev->io_queues[HCTX_TYPE_POLL],
+		     this_w_queues = dev->io_queues[HCTX_TYPE_DEFAULT];
+
+	if (!io_queues) {
+		dev->io_queues[HCTX_TYPE_POLL] = 0;
+		dev->io_queues[HCTX_TYPE_DEFAULT] = 0;
+		dev->io_queues[HCTX_TYPE_READ] = 0;
+		return;
+	}
+
+	if (this_p_queues >= io_queues)
+		this_p_queues = io_queues - 1;
+	irq_queues = io_queues - this_p_queues;
+
+	if (this_w_queues > irq_queues)
+		this_w_queues = irq_queues;
+
+	dev->io_queues[HCTX_TYPE_POLL] = this_p_queues;
+	dev->io_queues[HCTX_TYPE_DEFAULT] = this_w_queues;
+	dev->io_queues[HCTX_TYPE_READ] = irq_queues - this_w_queues;
+}
+
 static int nvme_create_io_queues(struct nvme_dev *dev)
 {
 	unsigned i, max, rw_queues;
@@ -1761,6 +1785,13 @@ static int nvme_create_io_queues(struct nvme_dev *dev)
 			break;
 	}
 
+	/*
+	 * If we've created less than expected io queues, redistribute the
+	 * dev->io_queues[] types accordingly.
+	 */
+	if (dev->online_queues - 1 != dev->max_qid)
+		nvme_distribute_queues(dev, dev->online_queues - 1);
+
 	/*
 	 * Ignore failing Create SQ/CQ commands, we can continue with less
 	 * than the desired amount of queues, and even a controller without
@@ -2185,11 +2216,6 @@ static int nvme_setup_io_queues(struct nvme_dev *dev)
 	result = max(result - 1, 1);
 	dev->max_qid = result + dev->io_queues[HCTX_TYPE_POLL];
 
-	dev_info(dev->ctrl.device, "%d/%d/%d default/read/poll queues\n",
-					dev->io_queues[HCTX_TYPE_DEFAULT],
-					dev->io_queues[HCTX_TYPE_READ],
-					dev->io_queues[HCTX_TYPE_POLL]);
-
 	/*
 	 * Should investigate if there's a performance win from allocating
 	 * more queues than interrupt vectors; it might allow the submission
@@ -2203,7 +2229,15 @@ static int nvme_setup_io_queues(struct nvme_dev *dev)
 		return result;
 	}
 	set_bit(NVMEQ_ENABLED, &adminq->flags);
-	return nvme_create_io_queues(dev);
+	result = nvme_create_io_queues(dev);
+
+	if (!result)
+		dev_info(dev->ctrl.device, "%d/%d/%d default/read/poll queues\n",
+					dev->io_queues[HCTX_TYPE_DEFAULT],
+					dev->io_queues[HCTX_TYPE_READ],
+					dev->io_queues[HCTX_TYPE_POLL]);
+	return result;
+
 }
 
 static void nvme_del_queue_end(struct request *req, blk_status_t error)
-- 
2.14.4